The major seral event in Yellowstone National Park and the
surrounding area is fire. For this reason, many of the vegetative
species in the ecosystem are those with abilities to thrive
under this kind of pressure.
Douglas-fir (Pseudotsuga mensezii) is a self-pruning
species with thick bark, and fast growth. The thick bark
helps protect the trees cambium from the intense heat of the
fire thus allowing the tree to survive and grow. Self-pruning
affords Douglas-fir safety from ground fires by preventing
fire ladders. Fast growth allows the tree to grow to the
states were it is able to use the prior traits.
Lodge-pole pine (Pinus contorta) is a thin-barked
species with very well developed fire ladders making it very
susceptible to fire damage and death. However, the seed biology
of the tree helps to ensure that it remain after an intense
fire. Lodge-pole pine has serrotinous cones. These cones
are held closed until temperature exceeds 140oF
at which time the seeds open and flood the area. Lodge-pole
pine also has normal seeds for times when fire is rare.
Quaking Aspen (Populus tremuloides), while possessing
neither thick bark, nor serrotinous cones, uses its ability
to sprout from unburned roots to continue itself. Fires very
rarely burn or damage the underground root system of large
plants and hence the Aspen is able to vigorously resprout
after a fire.
Forbes and grasses are usually the first to populate a disturbed
area and do so via wind blown seeds that come from area of
the park and surrounding ecosystem that were undamaged by
fire. Many of these species help to prepare the soil for
larger, later seral species as well as feed the variety of
wildlife of the park in the summer.